1999 DODGE NEON ESP

HEX
CODEGENERIC
SCAN
TOOL
CODEDRB SCAN TOOL
DISPLAYDESCRIPTION OF DIAGNOSTIC TROUBLE CODE
20 P0134 Right Rear (or just)
Upstream O2S Stays at
CenterNeither rich or lean condition detected from the oxygen
sensor.
21* P1281 Engine Is Cold Too Long Engine did not reach operating temperature within
acceptable limits.
23 P0500 No Vehicle Speed Sensor
SignalNo vehicle speed sensor signal detected during road
load conditions.
24 P0107 MAP Sensor Voltage Too
LowMAP sensor input below minimum acceptable voltage.
25 P0108 MAP Sensor Voltage Too
HighMAP sensor input above maximum acceptable voltage.
27 P1297 No Change in MAP From
Start to RunNo difference recognized between the engine MAP
reading and the barometric (atmospheric) pressure
reading from start-up.
28* P0320 No Crank Reference
Signal at PCMNo crank reference signal detected during engine
cranking.
2A P0352 Ignition Coil #2 Primary
CircuitPeak primary circuit current not achieved with maximum
dwell time.
2B P0351 Ignition Coil #1 Primary
CircuitPeak primary circuit current not achieved with maximum
dwell time.
2C* P1389 No ASD Relay Output
Voltage at PCMAn Open condition Detected In The ASD Relay Output
Circuit.
2E P0401 EGR System Failure Required change in air/fuel ratio not detected during
diagnostic test.
30* P1697 PCM Failure SRI Miles
Not StoredUnsuccessful attempt to update EMR mileage in the
PCM EEPROM
31 P1696 PCM Failure EEPROM
Write DeniedUnsuccessful attempt to write to an EEPROM location
by the PCM.
39 P0112 Intake Air Temp Sensor
Voltage LowIntake air temperature sensor input below the maximum
acceptable voltage.
3A P0113 Intake Air Temp Sensor
Voltage HighIntake air temperature sensor input above the minimum
acceptable voltage.
3C P0106 Barometric Pressure Out
of RangeMAP sensor has a baro reading below an acceptablr
level.
3D P0204 Injector #4 Control Circuit Injector #4 output driver does not respond properly to
the control signal.
3E P0132 Right Rear (or just)
Upstream O2S Shorted to
VoltageOxygen sensor input voltage maintained above the
normal operating range.
44 P0600 PCM Failure SPI
CommunicationsPCM Internal fault condition detected.
52 P1683 S/C Power Relay Ckt An open or shorted condition detected in the speed
control servo power control circuit
65* P1282 Fuel Pump Relay Control
CircuitAn open or shorted condition detected in the fuel pump
relay control circuit.
25 - 4 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

HEX
CODEGENERIC
SCAN
TOOL
CODEDRB SCAN TOOL
DISPLAYDESCRIPTION OF DIAGNOSTIC TROUBLE CODE
66 P0133 Right Bank Upstream O2S
Slow ResponseOxygen sensor response slower than minimum required
switching frequency.
67 P0135 Right Rear (or just)
Upstream O2S Heater
FailureUpstream oxygen sensor heating element circuit
malfunction.
69 P0141 Right Rear (or just)
Downstream O2S Heater
FailureOxygen sensor heating element circuit malfunction.
6A P0300 Multiple Cylinder Mis-fire Misfire detected in multiple cylinders.
6B P0301 Cylinder #1 Mis-fire Misfire detected in cylinder #1.
6C P0302 Cylinder #2 Mis-fire Misfire detected in cylinder #2.
6D P0303 Cylinder #3 Mis-fire Misfire detected in cylinder #3.
6E P0304 Cylinder #4 Mis-fire Misfire detected in cylinder #4.
70 P0420 Right Rear (or just)
Catalyst Efficency FailureCatalyst efficiency below required level.
71 P0441 Incorrect Pruge Flow Insufficient or excessive vapor flow dtected during
evaporation emission system operation.
72 P1899 P/N Switch Stuck in Park
or in GearIncorrect input state detected for the Park/Neutral
switch, auto. trans. only.
73* P0551 Power Steering Switch
FailurePower steering high pressure seen at high speed (2.5L
only).
76 P0172 Right Rear (or just) Fuel
System RichA rich air/fuel mixture has been indicated by an
abnormally lean correction factor.
77 P0171 Right Rear (or just) Fuel
System LeanA lean air/fuel mixture has been indicated by an
abnormally rich correction factor.
7E P0138 Right Rear (or just)
Downstream O2S Shorted
to VoltageOxygen sensor input voltage maintained above the
normal operating range.
80 P0125 Closed Loop Temp Not
ReachedEngine does not reach 20ÉF within 5 minutes with a
vehicle speed signal.
81 P0140 Right Rear (or just)
Downstream O2S Stays at
CenterNeither reich or lean condition detected from the
downstream oxygen sensor.
84 P0121 TPS Voltage Does Not
Agree With MAPTPS signal does not correlate to MAP sensor.
85 P1390 Timing Belt Skipped 1
tooth or MoreRelationship between Cam and Crank signal is not
correct.
8A P1294 Target Idle Not Reached Actual idle speed does not equal target idle speed.
91 P1299 Vacuum Leak Found (IAC
Fully Seated)MAP sensor signal does not correlate to throttle position
sensor signal. Possible vacuum leak.
92 P1496 5 Volt Supply Output Too
Low5 volt output from regulator does not meet minimum
requirement.
94* P0740 Torq Conv Clu, No RPM
Drop At LockupRelationship between engine speed and vehicle speed
indicates no torque converter clutch engagement (auto.
trans. only).
PLEMISSION CONTROL SYSTEMS 25 - 5
DESCRIPTION AND OPERATION (Continued)

HEX
CODEGENERIC
SCAN
TOOL
CODEDRB SCAN TOOL
DISPLAYDESCRIPTION OF DIAGNOSTIC TROUBLE CODE
95* P0462 Fuel Level Sending Unit
Volts Too LowOpen circuit between PCM and fuel gauge sending unit.
96* P0463 Fuel Level Sending Unit
Volts Too HighCircuit shorted to voltage between PCM and fuel gauge
sending unit.
97* P0460 Fuel Level Unit No
Change Over MilesNo movement of fuel level sender detected.
98 P0703 Brake Switch Stuck
Pressed or ReleasedNo release of brake switch seen after too many
accelerations.
99 P1493 Ambient/Batt Temp Sen
VoltsToo LowBattery temperature sensor input voltage below an
acceptable range.
9A P1492 Ambient/Batt Temp Sensor
VoltsToo HighBattery temperature sensor input voltage above an
acceptable range.
9B P0131 Right Rear (or just)
Upstream O2S Shorted to
GroundO2 sensor voltage too low, tested after cold start.
9C P0137 Right Rear (or just)
Downstream O2S Shorted
to GroundO2 sensor voltage too low, tested after cold start.
9D P1391 Intermittent Loss of CMP
or CKPIntermittent loss of either camshaft or crankshaft
position sensor.
AO PO442 Evap Leak Monitor Small
Leak detectedA small leak has been detected by the leak detection
monitor.
A1 PO455 Evap Leak Monitor Large
Leak DetectedThe leak detection monitor is unable to pressurize Evap
system, indicating a large leak.
B7 P1495 Leak DetectionPump
Soleniod CircuitLeak detection pump soleniod circuit fault (open or
Short).
B8 P1494 Leak detect Pump Sw or
Mechanical FaultLeak detection pump switch does not respond to input.
BA P1398 Mis-fire Adaptive
Numerator at LimitCKP sensor target windows have too much variation.
BB P1486 Evap Hose Pinched A pinched or bent Evap hose.
CO P1195 Cat Mon Slow O2
UpstreamOxygen sensor response slower than minimum required
switching frequency.
MONITORED SYSTEMS
There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor-
mance. These monitors use information from various
sensor circuits to indicate the overall operation of the
fuel, engine, ignition and emission systems and thus
the emissions performance of the vehicle.
The fuel, engine, ignition and emission systems
monitors do not indicate a specific component prob-
lem. They do indicate that there is an implied prob-
lem within one of the systems and that a specific
problem must be diagnosed.If any of these monitors detect a problem affecting
vehicle emissions, the Malfunction Indicator (Check
Engine) Lamp will be illuminated. These monitors
generate Diagnostic Trouble Codes that can be dis-
played with the check engine lamp or a scan tool.
The following is a list of the system monitors:
²EGR Monitor
²Misfire Monitor
²Fuel System Monitor
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Catalyst Monitor
²Evaporative System Leak Detection Monitor
25 - 6 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

Following is a description of each system monitor,
and its DTC.
Refer to the appropriate Powertrain Diagnos-
tics Procedures manual for diagnostic proce-
dures.
HEX 66, and 7AÐOXYGEN SENSOR (O2S)
MONITOR
Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperature 300É to 350ÉC (572É to 662ÉF), the
sensor generates a voltage that is inversely propor-
tional to the amount of oxygen in the exhaust. The
information obtained by the sensor is used to calcu-
late the fuel injector pulse width. This maintains a
14.7 to 1 air fuel (A/F) ratio. At this mixture ratio,
the catalyst works best to remove hydrocarbons (HC),
carbon monoxide (CO) and nitrous oxide (NOx) from
the exhaust.
The O2S is also the main sensing element for the
EGR, Catalyst and Fuel Monitors.
The O2S may fail in any or all of the following
manners:
²Slow response rate
²Reduced output voltage
²Dynamic shift
²Shorted or open circuits
Response rate is the time required for the sensor to
switch from lean to rich once it is exposed to a richer
than optimum A/F mixture or vice versa. As the sen-
sor starts malfunctioning, it could take longer to
detect the changes in the oxygen content of the
exhaust gas.
The output voltage of the O2S ranges from 0 to 1
volt. A good sensor can easily generate any output
voltage in this range as it is exposed to different con-
centrations of oxygen. To detect a shift in the A/F
mixture (lean or rich), the output voltage has to
change beyond a threshold value. A malfunctioning
sensor could have difficulty changing beyond the
threshold value.
HEX 67, 69, 7C, and 7DÐOXYGEN SENSOR
HEATER MONITOR
If there is an oxygen sensor (O2S) DTC as well as
a O2S heater DTC, the O2S fault MUST be repaired
first. After the O2S fault is repaired, verify that the
heater circuit is operating correctly.
Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperature 300É to 350ÉC (572 Éto 662ÉF), the
sensor generates a voltage that is inversely propor-
tional to the amount of oxygen in the exhaust. Theinformation obtained by the sensor is used to calcu-
late the fuel injector pulse width. This maintains a
14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio,
the catalyst works best to remove hydrocarbons (HC),
carbon monoxide (CO) and nitrogen oxide (NOx) from
the exhaust.
The voltage readings taken from the O2S are very
temperature sensitive. The readings are not accurate
below 300ÉC. Heating of the O2S is done to allow the
engine controller to shift to closed loop control as
soon as possible. The heating element used to heat
the O2S must be tested to ensure that it is heating
the sensor properly.
The O2S circuit is monitored for a drop in voltage.
The sensor output is used to test the heater by iso-
lating the effect of the heater element on the O2S
output voltage from the other effects.
HEX 2EÐEGR MONITOR
The Powertrain Control Module (PCM) performs
an on-board diagnostic check of the EGR system.
The EGR system consists of two main components:
a vacuum solenoid back pressure transducer and a
vacuum operated valve. The EGR monitor is used to
test whether the EGR system is operating within
specifications. The diagnostic check activates only
during selected engine/driving conditions. When the
conditions are met, the EGR is turned off (solenoid
energized) and the O2S compensation control is mon-
itored. Turning off the EGR shifts the air fuel (A/F)
ratio in the lean direction. The O2S data should indi-
cate an increase in the O2 concentration in the com-
bustion chamber when the exhaust gases are no
longer recirculated. While this test does not directly
measure the operation of the EGR system, it can be
inferred from the shift in the O2S data whether the
EGR system is operating correctly. Because the O2S
is being used, the O2S test must pass its test before
the EGR test.
HEX 6A,6B, 6C, 6D, 6E, AE, and AFÐMISFIRE
MONITOR
Excessive engine misfire results in increased cata-
lyst temperature and causes an increase in HC emis-
sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank-
shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.
HEX 76, 77, 78, and 79ÐFUEL SYSTEM
MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
PLEMISSION CONTROL SYSTEMS 25 - 7
DESCRIPTION AND OPERATION (Continued)

system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even-
tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .020º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases due
to the flow through the purge system, the leak check
portion of the diagnostic is complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.
TRIP DEFINITION
A ªTripº means vehicle operation (following an
engine-off period) of duration and driving mode such
that all components and systems are monitored at
least once by the diagnostic system. The monitors
must successfully pass before the PCM can verify
that a previously malfunctioning component is meet-
ing the normal operating conditions of that compo-
nent. For misfire or fuel system malfunction, the
MIL may be extinguished if the fault does not recur
when monitored during three subsequent sequential
driving cycles in which conditions are similar to
those under which the malfunction was first deter-
mined.
Anytime the MIL is illuminated, a DTC is stored.
The DTC can self erase only when the MIL has been
extinguished. Once the MIL is extinguished, the
PCM must pass the diagnostic test for the most
recent DTC for 40 warm-up cycles (80 warm-up
cycles for the Fuel System Monitor and the Misfire
Monitor). A warm-up cycle can best be described by
the following:
²The engine must be running²A rise of 40ÉF in engine temperature must occur
from the time when the engine was started
²Engine coolant temperature must reach at least
160ÉF
²A ªdriving cycleº that consists of engine start up
and engine shut off.
Once the above conditions occur, the PCM is con-
sidered to have passed a warm-up cycle. Due to the
conditions required to extinguish the MIL and erase
the DTC, it is most important that after a repair has
been made, all DTC's be erased and the repair veri-
fied.
COMPONENT MONITORS
There are several components that will affect vehi-
cle emissions if they malfunction. If one of these com-
ponents malfunctions the Malfunction Indicator
Lamp (Check Engine) will illuminate.
Some of the component monitors are checking for
proper operation of the part. Electrically operated
components now have input (rationality) and output
(functionality) checks. Previously, a component like
the Throttle Position sensor (TPS) was checked by
the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there
is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
greater or lesser throttle opening than MAP and
engine rpm indicate. In the case of the TPS, if engine
vacuum is high and engine rpm is 1600 or greater
and the TPS indicates a large throttle opening, a
DTC will be set. The same applies to low vacuum
and 1600 rpm.
Any component that has an associated limp in will
set a fault after 1 trip with the malfunction present.
Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Power-
train Diagnostic Procedure Manual for diagnostic
procedures.
NON-MONITORED CIRCUITS
The PCM does not monitor all circuits, systems
and conditions that could have malfunctions causing
driveability problems. However, problems with these
systems may cause the PCM to store diagnostic trou-
ble codes for other systems or components. For exam-
ple, a fuel pressure problem will not register a fault
directly, but could cause a rich/lean condition or mis-
fire. This could cause the PCM to store an oxygen
sensor or misfire diagnostic trouble code.
The major non-monitored circuits are listed below
along with examples of failures modes that do not
directly cause the PCM to set a DTC, but for a sys-
tem that is monitored.
PLEMISSION CONTROL SYSTEMS 25 - 9
DESCRIPTION AND OPERATION (Continued)

INTERNATIONAL VEHICLE CONTROL AND DISPLAY
SYMBOLS
INTERNATIONAL VEHICLE CONTROL AND
DISPLAY SYMBOLS
The graphic symbols illustrated in the following
chart (Fig. 3) are used to identify various instrument
controls. The symbols correspond to the controls and
displays that are located on the instrument panel.
FASTENER IDENTIFICATION
FASTENER IDENTIFICATION
THREAD IDENTIFICATION
SAE and metric bolt/nut threads are not the same.
The difference is described in the Thread Notation
chart (Fig. 4).
GRADE/CLASS IDENTIFICATION
The SAE bolt strength grades range from grade 2
to grade 8. The higher the grade number, the greaterthe bolt strength. Identification is determined by the
line marks on the top of each bolt head. The actual
bolt strength grade corresponds to the number of line
marks plus 2. The most commonly used metric bolt
strength classes are 9.8 and 12.9. The metric
strength class identification number is imprinted on
the head of the bolt. The higher the class number,
the greater the bolt strength. Some metric nuts are
imprinted with a single-digit strength class on the
nut face. Refer to the Fastener Identification and
Fastener Strength Charts.
INTERNATIONAL CONTROL AND DISPLAY SYMBOLS
Fig. 3
Fig. 4 Thread NotationÐSAE and Metric
PLINTRODUCTION 5
GENERAL INFORMATION (Continued)